Total Scattering Cross-Section of Twin Circular Silver Nanowires Excited by Electron Beam Moving between Them

We consider the effect of diffraction radiation, which accompanies the motion of a modulated beam of electrons between a pair of identical silver nanowires, in the optical range of modulation frequencies. The electromagnetic field of such a two-dimensional beam is shaped as a surface wave propagating along its trajectory with the phase velocity equal to the beam velocity. This wave induces the currents on the obstacles and hence a radiation occurs even if the beam does not touch the obstacle. Here, a pair of silver nanowires behaves as an open plasmonic resonator, thanks to which the diffraction radiation is enhanced near the wavelengths of the natural modes. We compute spectral characteristics of this resonator, visualize the far field patterns, and analyze their dependence on electron beam parameters.